There are three categories of ethos.
- phronesis - practical skills & wisdom
- arete - virtue, goodness
- eunoia - goodwill towards the audience
In a sense, ethos does not belong to the speaker but to the audience. Thus, it is the audience that determines whether a speaker is a high- or a low-ethos speaker. Violations of ethos include:
- The speaker has a direct interest in the outcome of the debate (e.g. a person pleading innocence of a crime);
- The speaker has a vested interest or ulterior motive in the outcome of the debate;
- The speaker has no expertise (e.g. a lawyer giving a speech on space flight is less convincing than an astronaut giving the same speech).
Completely dismissing an argument based on any of the above violations of ethos is a formal fallacy, rendering the dismissal of the argument invalid.
The term "source credibility" has been used as the construct examined in the social sciences. Though recent work has found support for the existence of the three dimensions identified above, work from the 1950s through the 1980s consistently revealed two dimensions (competence and character) with other dimensions such as dynamism found only when broad approaches equating credibility with "person perception" were taken.
